Women exposed while in the womb to low levels of a common stain repellent are three times as likely to gain more weight and have large waists as young adults than women less exposed during development. This is the first time that this chemical, known as PFOA, has been linked to obesity in humans.

Women exposed to low levels of a common stain repellent while in the womb are three times as likely to gain more weight and have large waists as young adults than women less exposed during development. Meanwhile, the results of the two-decade study found no link between men’s obesity and prenatal exposure to the chemical known as PFOA.

The study is published in the journal Environmental Health Perspectives.

While this is the first time that PFOA has been linked directly to obesity in humans, this study was initiated explicitly because work with mice showed that low doses of PFOA can cause weight gains in post-pubertal female mice exposed in the womb. This work raises further concerns that chemical exposures in the womb – even at low concentrations – may play a role in the ongoing obesity epidemic in people.

In the last decades, obesity rates in children and adults worldwide have skyrocketed. The accompanying societal effects – which can include health problems such as diabetes and heart disease – have experts concerned. Processed foods, less activity and exposure to environmental chemicals may contribute to the problem.

This human study coincides with results from a recent animal study. Researchers found a link between prebirth exposures and weight gain in the female but not the male offspring.

The chemical PFOA – also known as C8 – is used to manufacture non-stick pans and water-resistant clothing. It is also found in some food packaging – such as microwave popcorn bags – as well as stain-resistant carpets, carpet-cleaning solutionsand some paints. Related chemicals used in fast food packaging may also turn into PFOA once they are absorbed into the body.

Because of its common use, PFOA is found in virtually everyone’s blood. Several U.S. companies have agreed to reduce the use of PFOA and related chemicals by 2015. However, exposures are expected to continue for a long time, because the chemicals already contaminate homes and food and break down very slowly.

Researchers measured levels of PFOA and other related fluorinated chemicals in blood samples collected from 665 pregnant Danish women in 1988 and 1989. Twenty years later, these levels were compared to body mass index (BMI), waist circumference and blood levels of related hormones in their daughters and sons. They adjusted for socioeconomic, personal habits and other factors that might also influence weight gain in the children.

They found that women exposed to the highest PFOA levels in the womb were three times more likely to be overweight or obese at age 20 compared to women with the lowest pre-birth exposures. The higher-exposed women were also three times more likely to have a large waist circumference compared to the less-exposed women. No effects were found in men, or for the other examined chemicals.

In women, higher PFOA levels were also associated with higher levels of leptin and insulin and lower levels of adiponectin – three important hormones for regulating body weight. Hormone effects in men were similar, but with weaker associations.

Further research is needed to better understand the links between early chemical exposures and obesity since other chemicals such as bisphenol A – which is used widely in hard plastics, food and beverage cans and cash-register receipts – are also potential obesogens.